Characterization of LhSorP5CS, a gene catalyzing proline synthesis in Oriental hybrid lily Sorbonne: molecular modelling and expression analysis

Background: Abiotic stresses negatively affect plant growth and flower production. In plants, P5CS proteins are key enzymes that catalyzed the rate-limiting steps of proline synthesis, and proline is a well-known osmoprotectant that is closely related to abiotic stress tolerance. However, information about the P5CS genes, their effects on proline accumulation, and their role in abiotic stress tolerance in Lilium is still lacking. Results: We isolated and characterized a novel gene (LhSorP5CS) from Oriental hybrid lily cultivar Sorbonne. Phylogenetic analysis indicated that LhSorP5CS is a member of the P5CS family. The three-dimensional structure of LhSorP5CS predicted by homology modeling showed high similarity to its correspondant human P5CS template. Further gene expression analysis revealed that LhSorP5CS expression was up-regulated by NaCl, mannitol, and ABA, and that stress-exposed plants accumulated proline at a significantly higher level than in the control. Conclusions: LhSorP5CS characterized in this study is involved in proline synthesis in lily, and that it might play an important role in abiotic stress tolerance. However, there should be other P5CS homologues in the lily genome, and some of them could be highly stress-induced and more important for proline accumulation. Future studies on P5CS family genes would be of great importance to proline-related stress tolerance in lily.